The invention relates to a grinding machine, particularly a high-speed grinding machine, having a bench on which bearing brackets for a turbine rotor consisting of several stages and a grinding wheel head are arranged, rotatably about its axis, the turbine rotor being disposed in the bearing brackets and, rotatably about a spindle axis extending parallel to the rotor axis, at least one grinding wheel being disposed in a receiving device at the grinding wheel head. The grinding wheel head and the bearing brackets are adjustable with respect to one another in the axial direction of the bench, which is determined by the rotor axis, so that the blades of the successive phases of the turbine rotor can be ground successively.
Such a high-speed grinding machine is described in European patent document EP 1 491 289. In order to be able to work different types of phases, this machine has a grinding wheel head, which can be rotated by 180°, and has two grinding wheels arranged on opposite sides of the head. This is done so that, depending on the position of the grinding wheel head, in each case, one of the grinding wheels machines one phase of the turbine rotor. In this manner, rotors can be machined for which blades of two different materials are used, the grinding wheels, with respect to their composition, being adapted to the respective blade material to be machined. In order to be able to adapt the rotor still better to the different thermal stresses in the turbines, depending to which stage of the rotor the blades are assigned, the latter are also manufactured of more than two different materials or alloys so that, depending on the number of materials used, for finishing the rotor, a correspondingly increased number of grinding wheels are required which are adapted to the respective material. In order to implement the latter, it might be considered to increase the number of grinding wheels at the grinding wheel head so that all grinding wheels necessary for grinding the turbine rotor will be available at the grinding wheel head. However, this would have the disadvantage of further increasing its weight, so that the constructive expenditures that exist even in the case of a two-grinding-wheel head would have to be increased even more in order to be able to position the grinding wheel head with the high precision required for an exact grinding.
The invention is therefore based on the problem of creating a high-speed grinding machine that is capable of automatically machining a turbine by use of more than one grinding wheel in a highly precise manner.
For solving this problem, the invention provides a magazine for grinding wheels and an automatically operating grinding wheel changer.
In this case, the grinding wheel head has only one or, as required, several receiving devices for grinding wheels so that its weight is as low as possible, and it can be guided in a highly precise manner while its constructive expenditures are still low. The number of receiving devices is definitely lower than the number of grinding wheels required for the rotor machining. Depending on the requirements, the grinding wheels are therefore exchanged by use of the grinding wheel changer. Since the latter operates automatically, the grinding operation for all stages of the rotor can be programmed by use of a corresponding control.
One or more receiving devices for grinding wheels are therefore situated at the grinding wheel head, which receiving devices are equipped with grinding wheels from a magazine, as required, while exchanging the grinding wheels present at the grinding wheel head.
The grinding wheel changer is preferably arranged on a linear carriage, which can be moved in the axial direction. The guiding of the linear carriage takes place parallel to the bench, so that a short path can be implemented between the grinding wheel head and the magazine.
In order to be able to optimize the changing operation with respect to time, the grinding wheel changer has two or more, but preferably two, receiving devices. The receiving devices are arranged in a distributed manner or mutually opposite on a platform which, rotatably about a vertical axis, is held on the carriage. As a result, one receiving device can accommodate a grinding wheel from the magazine and the other receiving device can accommodate a grinding wheel from the grinding wheel head. The grinding wheel on the grinding wheel head is replaced by the grinding wheel from the magazine, before this grinding wheel itself is deposited in the magazine.
The magazine is preferably arranged on the face of the bench and, in a rotatable carrier, has several receiving devices for the grinding wheels, which are arranged in a plane oriented vertically and perpendicularly with respect to the axial direction. This arrangement permits short paths and therefore a change that can be carried out rapidly.
Furthermore, each grinding wheel has a coupling piece of a first type on its one face, which coupling piece interacts with a corresponding counterpart in the receiving devices at the grinding wheel head and the magazine carrier, and a coupling piece of a second type on its other face, which coupling piece interacts with the receiving devices at the grinding wheel changer.
The coupling piece of the first type has a long cone, which permits a precise and centric guidance and footing in the grinding wheel head.
With respect to the coupling of the second type, it should be taken into account that the grinding wheel at the grinding wheel head is largely encapsulated by a protective hood, which permits a sucking-off of the grinding dust. A wall of this protective hood rests closely against the free side of the grinding wheel. For taking into account the limited space conditions, the invention further provides that the coupling piece of the second type consists of a ring which is to be inserted in a face-side indentation of the grinding wheel core, the ring axis being situated in the grinding wheel axis, and the edge of the ring projecting from the face having a collar pointing radially toward the inside.
For this purpose, the counterpart in the receiving device at the grinding wheel changer consists of a ring-type indentation for receiving the ring. Clamping elements are provided at the interior edge of the indentation, which clamping elements can be moved radially toward the outside by way of a movement operation, in order to reach behind the collar on an inserted ring and to thereby close the coupling.
The operating of the clamping elements to place them into a position closing the coupling takes place by way of a tensioning device consisting of springs, and into a position releasing the coupling by way of a hydraulic or pneumatic adjusting device. In this manner, it is ensured that the coupling is mechanically closed and a grinding wheel held by the coupling is not released from the coupling even in the event of a failure of the electric or pneumatic supply of the grinding wheel changer.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.